Study shows virtual colonoscopy more accurate and less invasive

CHICAGO -- A procedure that lets doctors find abnormal growths in the colon through computer-generated images is slightly more accurate and less invasive than conventional colonoscopy, new research suggests.

Some patients found the so-called "virtual colonoscopy," in which doctors use a CT scanner to produce three-dimensional pictures for evaluation, less comfortable than standard colonoscopy. Critics also pointed out that if a growth is found, a conventional colonoscopy has to be performed anyway.

Despite that, researchers hope the benefits of the high-tech procedure will lead to more people getting screened for the growths, known as polyps. The American Cancer Society recommends that adults over 50 years of age get a colonoscopy every 10 years. Less than half of those who should get screened do so, the society estimates.

"Virtual colonoscopy is an accurate screening tool, and if our methods are used this hopefully will result in more widespread screening, especially for patients that avoid screenings," said lead author Dr. Perry J. Pickhardt. "If we can screen more patients, we know it will prevent cancers and save lives."

Colon cancer is the second leading cause of cancer-related deaths in the United States, resulting in nearly 60,000 deaths each year. The detection and removal of polyps can help reduce fatalities and prevent cancer from developing.

Differing methods

In a conventional colonoscopy, patients take laxatives to cleanse their bowels 24 hours before the procedure. Patients are sedated before an instrument is inserted through the rectum that allows doctors to screen and remove any suspicious growths.

In a virtual colonoscopy, patients also take laxatives but are not sedated. A small rectal catheter is inserted, and patients hold their breath as a CT scanner takes X-rays of the colon that result in images doctors can scan for polyps.

The virtual colonoscopy study was presented Monday in Chicago at the annual meeting of the Radiological Society of North America.

Researchers studied 1,233 adults who had an average risk of having colonic growths. Virtual colono-scopy found polyps that were at least 10 millimeters in diameter 93.8 percent of the time and discovered growths of at least 8 millimeters 93.9 percent of the time.

In comparison, conventional colonoscopy found polyps that were at least 10 millimeters in diameter 87.5 percent of the time and discovered growths of at least 8 millimeters 91.5 percent of the time.

The study also found virtual colonoscopy did not have many false positives.

In the study, 622 patients had polyps and two polyps were malignant.

Virtual colonoscopy detected both malignant polyps, but conventional colonoscopy only found one.

Critics say if a significant polyp is found during the virtual colonoscopy, a conventional colonoscopy then has to be performed to remove the polyp.

"That's two procedures as opposed to one. Since the patient has to go through the same preparation, which is the hardest part, they might as well do the conventional one," said Dr. Herman Kattlove, medical editor at the American Cancer Society.

Kattlove said that while the virtual colonoscopy could be a good screening device for the general population, the cancer society recommends conventional colonoscopy.

According to a survey of the study's patients, 54 percent said the virtual colonoscopy was more uncomfortable than the conventional colonoscopy, but researchers point out that's because virtual colonoscopy patients were not sedated.

Pickhardt, a radiology professor at the University of Wisconsin Medical School in Madison, considers the lack of sedation to be a benefit because patients do not spend any time in the recovery room.

"Neither procedure is a walk in the park, but virtual colonoscopy is significantly better tolerated," he said.